The present invention relates to model railroad train crossing gates and, more particularly, to apparatus for detecting the approach of a model train and activating the crossing gate in response thereto.
In model railroading great efforts are made to create toy railroad devices, e.g. trains, signals etc., which are as close to the real device as possible. With respect to grade crossing gates it is desirable to have the operation of the gates activated by the approach of the model train to the grade crossing, regardless of the direction from which the crossing is approached. As a result, a train detection system is needed which has this capability.
Of the prior art detection systems the track switch and reed switch systems are not considered to be bi-directional. A track switch system, such as that disclosed in U.S. Pat. No. 3,418,750 to Ryan et al., employs a contact member beneath or along side the tracks, which member is actuated by the weight of the locomotive or a shoe extending from its side, respectively. The operation of the switch causes a motor or an electrical coil (such as in U.S. Pat. No. 3,179,063 to Case et al. or U.S. Pat. No. 2,810,067 to Fowler), or a mechanical member as in the Ryan et al. patent to operate the crossing gate. With the reed switch system the same operation as with the track switch is accomplished via a magnetic reed relay activated by a magnet located on the train. Only one of the track or reed switches, positioned to one side of the grade crossing, is used in such a system because the switch itself cannot determine which way the train is moving. If an attempt were made to make this system bi-directional by placing such switches on both sides of the grade crossing along the tracks, the effort would be hampered by the fact that the gate would close both as the train approached the grade crossing and as it left the grade crossing.
With a series relay detection system a sensitive relay is connected in series with the power supply and the track. When power is applied to a block of track and a locomotive is in that block so as to draw current from the supply, the series relay operates. Such a system, while bi-directional, only detects the locomotive and it is expensive.
Electronic current measuring circuitry and optoelectronic detectors using photocells or infrared light sources and photo transistors are also bi-directional, but they are expensive and are so sensitive to current changes and light changes that their operations are erratic.
Once the presence of the train has been detected the gate must be operated in a manner resembling a real crossing gate. Typically real crossing gates are lowered slowly and are raised slowly, independent of the speed of the train. However, most model gates snap down and up rapidly, particularly those operated by an electrical coil or a mechanical member.
Some real life crossing gates are also equipped with two alternately flashing lights and a sounding bell which operate synchronously. However, the typical models available in the prior art either do not provide these features or are unable to operate them synchronously. Some systems use flashing lights controlled by complicated electronic devices which are expensive. Also the regular beat of a bell has been achieved by slow motion motors driving a cam equipped with teeth that act on the contacts of a micro-switch to operate the bell. See for example "Practical Electronic Projects For Model Railroads" by Thorne, Kalmbach Publishing Co. (1974), p. 69. Alternately there are prior art systems that create a bell sound electronically by mixing several tones. These systems, however, are also expensive.